Thermostat and method of adjusting the same

ABSTRACT

In a thermostat which comprises a first housing portion accommodating a circuit breaker and a second housing portion accommodating a snap action temperature sensor coupled to the circuit breaker by an actuating member, the two housing portions have mutually contacting camming faces shaped and arranged in such a manner that a coaxial rotation of the two housing portions with respect to one another varies the axial distance between the two housing portions and thus the distance between the snap action temperature sensor and the circuit breaker.

United States Patent [191 [111 3,882,440 Hollweck et al. May 6, 1975 [54] THERMOSTAT AND METHOD OF 2,753,421 7/1956 Mertler 337 347 ADJUSTING THE SAME 3,668,594 6/1972 Kulick 337/360 X [75] Inventors: Walter Hollweck; Karlheinz Eberl,

both of Nurnberg, Germany Primary Examiner-J. D. Miller [73] Assignee: Inter control, Hermann Kohler Assistant Examiner l,:red Bell Elektrik GmbH & Cm KG, Attorney, Agent, or Fzrm-Spencer & Kaye Nurnberg, Germany [22] Filed: Aug. 1, 1973 [57] ABSTRACT [21] Appl. N0.: 384,506

In a thermostat which comprises a first housing portion accommodating a circuit breaker and a second [30] Foreign Apphcanon Prmmy Data housing portion accommodating a snap action temper- Aug. 1, 1972 Germany .i 2237815 ature Sensor coupled to the circuit breaker by an actw ating member, the two housing portions have mutually [52] US. Cl. 337/354; 337/360 contacting camming faces Shaped and arranged in [51] hit. Cl. H0lh 37/52 Such a manner that a coaxial rotation of the two hous [58] Field of Search 337/305, 347, 354, 360, m portions with respect to one another varies the 337/361 380 axial distance between the two housing portions and thus the distance between the snap action temperature [56] References and sensor and the circuit breaker.

UNITED STATES PATENTS 2,230,770 2/1941 Almblo 337/354 X 8 Claims, 5 Drawing Figures PAIENTEDHAY' 6131s SHEET 1 BF 2 FIG. I

23 Ill M 38 l\ I T2 HGRADE) THERMOSTAT AND METHOD OF ADJUSTING THE SAME BACKGROUND OF THE INVENTION This invention relates to a thermostat which includes a snap action bimetal temperature sensor coupled by means of an insulating actuating member with the contact system of, for example, an electric circuit breaker. The temperature sensor, on the one hand, and the contact system, on the other hand, are arranged in two separate housing portions which have common contacting faces.

The invention further relates to a method of adjusting a thermostat of the afore-outlined type.

A bimetal temperature sensor of the snap action type generally comprises a circular, arcuate bimetal disc which first undergoes a so-called creeping expansion (or contraction) within a predetermined temperature interval and then, upon reaching a predetermined temperature, snaps in an impact-like manner from one position into another with a simultaneous reversal of the orientation of its curvature. During this snapping movement the disc executes a relatively large working stroke which, with the aid of an insulating actuating member, is used for the opening or closing of electric contacts. The latter may comprise, for example, a leaf spring contact and a stationary contact. Such snap action temperature sensor may also be formed of a bimetal strip corrugated over a portion of its width. Snap action temperature sensors find wide-range application since they make possible a simple and inexpensive manufacture of thermostats, particularly temperature regulators having a predetermined fixed switching point.

In order to obtain a fault-free functioning of the contact system in thermostats of the afore-outlined type, that is, to provide an instantaneous, non-creeping contact making or contact breaking by the snap action temperature sensor, it has to be ensured that the actuation of the contacts by means of the snap action temperature sensor occurs, in fact, in the course of the execution of the afore-noted large working stroke during the snap action and not during the afore-noted creeping deformation of the temperature sensor. In order to ensure the foregoing, it is necessary that the thermostat be accurately adjusted, that is, the distance between the snap action temperature sensor and the contact system be set with respect to the dimensions of the insulating actuating member in such a manner that during the creeping deformation of the temperature sensor, the contacts cannot be actuated. Stated differently, the distance between the contact system and the snap action body must be selected with respect to the length of the actuating member in such a manner that there is provided a sufficient clearance for the dimensional changes of the snap action body during its creeping deformation and that, during the snap action proper, the magnitude of the executed large work stroke is sufficient to open or close the contact system with the aid of the actuating member. Such an adjustment which is necessary for a fault-free operation of thermostats of the afore-outlined type has been accomplished heretofore, for example, by the insertion of actuating members of different lengths, or by bending the contact carriers or contact springs to a greater or lesser extent, or by turning a setscrew constituting the stationary contact or forming part of the actuating member. It has also been attempted to provide in switches of the aforenoted type, deformable housing portions which carry the contact system on the one hand and the bimetal element on the other hand, and to adjust the contact distance by mechanically deforming these components, for example, by pinching or the like.

All of the afore-mentioned modes of adjustment have certain disadvantages. Thus, the insertion of actuating members of different lengths requires a multiple disassembly and reassembly of the device and a new testing of each adjusted position. A bending of the contact carriers or contact spring is often unsatisfactory, since the position set by bending may not remain constant due to the resiliency of the bent material. Where adjustments are effected by turning threadedly engaging components, the adjusted position may change in response to vibration or jarring. An adjustment by deforming the housing portions has the disadvantage that the adjustment can be effected only as an additional step subsequent to the assembly of the thermostat, thus increasing the expenses of the manufacturing process. Further, housing portions, to be deformable for the foregoing purpose, have to be metallic components mounted instead of or between the usually plastic housing components. Thus, the manufacture of thermostats which are adjusted by deforming the housing components is complicated and expensive.

SUMMARY OF THE INVENTION It is an object of the invention to provide a thermostat of the afore-noted type which is free from the described disadvantages and which may be adjusted already during the mounting operation.

This object and others to become apparent as the specification progresses, is accomplished by the invention, according to which, briefly stated, those zones of the two housing portions which are in contact with one another are formed in such a manner that a coaxial turning of the two housing portions relative to one another varies the distance between the temperature sensor accommodated in the one housing portion and the contact system accommodated in the other housing portion.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating the displacement of a selected point on the snap action bimetal temperature sensor as a function of temperature.

FIG. 2 is a sectional side elevational view of a preferred embodiment of the invention.

FIG. 3 is an exploded perspective view of two components incorporated in the embodiment illustrated in FIG. 2.

FIG. 4 is a side elevational view, partially in section, of another preferred embodiment of the invention.

FIG. 5 is a perspective view of still another preferred embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning first to FIG. 1, there is shown a diagram illustrating the displacement (ordinate) of a selected point on a snap action bimetal temperature sensor as a function of temperature (abscissa). More specifically, the diagram illustrates the path of deformation of a snap action disc in a predetermined temperature zone which includes that temperature at which the snapping movement proper takes place. It is noted that the diagram is qualitative only, since actual temperature and distance values vary from case to case. The diagram, which, regarding illustration and information conveyed, is known to persons skilled in the art and which may be supplied, for example, by the manufacturer, shows in the temperature zone from T to but excluding T the creeping expansion (in the lower portion of the ordinate) and in the temperature zone from T to but excluding T the creeping contraction (in the upper part of the ordinate) of the snap action disc. The temperature T in case of increasing temperatures and the temperature T in case of dropping temperature are the snap action temperatures at which the disc snaps in an impact-like manner in a direction opposite to the orientation of the previously assumed curved shape. During this occurrence, as it may be observed from FIG. 1, there is executed a relatively large displacement which may beutilized as a working stroke for operating the contact system of a circuit breaker with the aid of an insulating actuating member which couples the snap action temperature sensor with a movable contact. In order to accomplish an instantaneous contact actuation in thethermostat according to the invention and thus securely exclude the possibility of a creeping contact actuation, it is required that the contact actuation be effected by the snap action disc as it travels from s to s (or from s to s that is, during the working stroke of its snapping movement and not during the creeping change in dimension, which, in each case, is situated timewise before the above-defined displacement range s s To ensure such an instantaneous contact actuation, it is necessary to adjust the thermostat. Such an adjustment is accomplished by setting the distance between the snap action disc and the contact system with respect to the length of the actuating member disposed therebetween in such a manner that in the zone of the creeping dimensional change, such a change does not yet cause an actuation of the contact system; such an actuation occurs only during the much more substantial dimensional change to which the disc is submitted during the snap action proper. In practice, in order to ensure a certain safety clearance, the thermostat is adjusted to utilize the work stroke portion s s which lies within the maximum available work stroke zone s The adjustment of the thermostat according to the invention is effected by coaxially rotating the two housing portions with respect to one another until a relative position between the two housing portions is reached in which the snap action disc opens or closes the contacts, for example, at room temperatures. The setting to the higher or lower desired value at which the thermostat according to the invention, should in fact switch, is then effected according to the disc characteristic represented by a diagram such as shown in FIG. 1. From this diagram, one may then read the distance through which the disc will move between room temperature and desired switching temperature. Assuming that a snap action disc, having the characteristics as shown in the diagram of FIG. 1, should switch, for example, at temperature T then after adjusting the thermostat to the room temperature T the distance between the snap action disc and the contact system has to be extended by the path from s to s, in order to ensure that in the temperature zone between T and up to and excluding T no contact actuation takes place, since in this temperature range the movement of the snap action disc from s to s is in fact the creeping deformation. In practice, as it was mentioned before, when the distance between the contact system and the temperature sensor is set, there is taken into account not only a path extending from s to s but the somewhat greater distance extending from s to s, in order to ensure that the switching operation in fact occurs during the work stroke of the snap action disc as the latter performs its snapping movement. This additional change in distance between the snap action disc and the contact system is effected by further turning the two housing portions relative to one another. The required extent of angular displacement for obtaining the afore-noted distance increased by s s is determined by the characteristics of the contacting faces of the housing portions, for example, the pitch of wedgeshaped parts of the housing portions. In this manner the function between the distance of the snap action disc from the contact system and the relative displacement of the two housing portions is known.

Turning now to FIG. 2, there is shown a preferred embodiment of the invention which comprises a first housing portion 1 accommodating two stationary contacts 2 and 3 connected, respectively, to electric conductors 4 and 5. There is further provided a reciprocable movable contact in the form of a bridge member 6 which, dependent on its position, electrically connects the contacts 2 and 3 to, or disconnects them from, one another. The bridge 6 is urged into engagement with the contacts 2, 3 by a compression spring 1 1. In a second housing portion 7, which is connected to the first housing portion 1 by means of a crimped cap 8, there is disposed a bimetal snap action disc 9 which, in its condition depicted in FIG. 2, is downwardly convex. The cap 8 is preferably made of a good heat conducting material to ensure rapid and true temperaturetransmission from the surrounding medium to the disc 9. The coupling between the snap action disc 9 and the movable contact bridge 6 is effected by means of an insulating actuating or force transmitting member 10, which is arranged in the housing portion 7 in such a manner that when the bridge 6 is in engagement with the L-shaped lower bent portions of the contacts 2 and 3, the upper end of the actuating member 10 is at a predetermined distance from the bridge 6. This distance, which is well observable in FIG. 2, corresponds, for example, to the path extending from s to s in the diagram of FIG. 1 and permits a creeping expansion of the snap action disc 9 during temperature increase in the temperature zone extending from T up to and excluding T without an actuation of the contact system. Such an actuation occurs at the temperature T as the contact bridge 6 is, against the action of spring 11, lifted off the contacts 2 and 3 by the actuating member 10 during the snapping movement of the disc 9. As a result, electric connection between contacts 2 and 3 is interrupted. The disc 9, upon completion of its snap action in response to a temperature increase, assumes an upwardly convex shape.

In case of a subsequent temperature drop, the ther mostat operates in a reverse manner. During such a drop, upon reaching the snap action temperature T the disc 9 snaps again into its position shown in FIG. 2, whereby the bridge 6 again connects the contacts 2 and 3 with one another under the action of the spring 11.

In the embodiment illustrated in FIG. 2, the contacting housing faces 12 and 13 of the two respective housing portions 1 and 7 constitute a pair of camming faces and are of wedge-shaped configuration as it may be better observed from the perspective FIG. 3 to be described later.

' The distance between the contact system in the housing portion 1 and the temperature sensor 9 in the housing portion 7 may be varied in a simple manner by a coaxial rotation of the housing portions 1 and 7 with respect to one another. Such a relative rotary motion will cause, due to the camming action of the cooperating faces 12 and 13, a shift in the axial distance between the two housing portions 1 and 7 and thus, as a result, a distance between the temperature sensor 9 and the movable contact 6 will vary. When the desired distance is reached, the cap 8 is crimped, whereby the housing portions 1 and 7 are tightened together. By appropriate means it is ensured that subsequent to the tightening together of the two housing portions 1 and 7 no further relative displacement therebetween can take place. For this purpose, on those parts of the two housing portions 1 and 7 which are covered by the cap 8, there may be provided one or more openings or grooves into which the cap 8 may extend after crimping the cap 8 over the edges of the housing portion 1. Thus, in this manner a mechanical connection between the housing portions 1 and 7 is ensured which prevents relative rotation with respect to one another. In the embodiment shown in changed by virtue of the camming action between the cooperating faces 12 and 13. As it may be further observed in FIG. 3, the two housing portions 1 and 7 have a cylindrical configuration at least in the zone of their mutually contacting faces 12 and 13, respectively. The wedge-shaped or stepped zones are arranged on the radial annular zones of the contacting faces and have oppositely oriented pitches with respect to the axes of the housing portions.

In FIG. 4 there is illustrated a further embodiment of the invention in which the wedge-shaped zones of the contacting faces 12 and 13 are formed as immediately successive wedge-shaped parts 12', 12", 12", and 13,

. 13", 13", forming three pairs of cooperating camming faces. In other respects, the embodiment shown in FIG. 4 corresponds to that illustrated in FIG. 2.

It is expedient to design the pitch (elevation) of the wedge-shaped zones or partial zones in such a manner that upon coaxially rotating the two housing portions 1 and 7 with respect to one another by moving one wedge-shaped zone or partial zone always on the same associated wedge-shaped zone or partial zone of the other housing portion, the maximum distance alteration required for the adjustment may be achieved. In such a case the crests of the wedge-shaped partial zones are disposed in one plane.

Turning now to FIG. 5, there is illustrated in a schematic perspective view still another embodiment of the invention. According to this embodiment, the mutually contacting cooperating faces of the two housing portions 1 and 7 have a stepped shape and have oppositely oriented pitches. The height of each step corresponds to the smallest possible adjustment step (increment). Thus, for example, if it is desired to increase the axial distance between the two housing portions by two steps, the housing protions are axially pulled apart and then, for example, the housing portion 7 is held stationary and the housing portion 1 is turned counterclockwise through an angle corresponding to two steps. Thereafter the two housing portions are secured together by the cap 8 (not shown in FIG. 5) as in the embodiment described in connection with FIG. 2. It is noted that from the exemplary relative position of the housing portions illustrated in FIG. 5, the axial distance therebetween may be increased by as many as three steps, or it may be decreased by one step.

It is a significant advantage of the thermostat and the method of its assembly according to the invention, that the adjustment of the thermostat may be effected as a one step operation during and part of the assembly and thus no additional adjusting operation subsequent to the completion of the assembly operation is required.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

We claim:

1. In a thermostat having a first and a second housing portion each having an axis, securing means for holding the two housing portions together, a circuit breaker held in the first housing portion, a snap action temperature sensor held in the second housing portion, an insulating actuating member coupling the temperature sensor to the circuit breaker, the improvement comprising at least one pair of camming faces, said pair being formed of two mutually engaging cooperating faces, one belonging to the one housing portion and the other belonging to the other housing portion, said camming faces being arranged for varying the axial spacing of the two housing portions and the distance between said circuit breaker and said temperature sensor upon coaxial rotation of the two housing portions with respect to one another.

2. A thermostat as defined in claim 1, wherein said cooperating camming faces have oppositely oriented, wedge-shaped configurations.

3. A thermostat as defined in claim 2, wherein each housing portion has a plurality of wedge-shaped camming faces to form a plurality of said pairs.

4. A thermostat as defined in claim 3, wherein said plurality of wedge-shaped camming faces are arranged in immediate succession on each housing portion.

5. A thermostat as defined in claim 1, wherein said camming faces have a stepped configuration and the cooperating stepped faces have a mutually oppositely 7 8 b. mounting a snap action temperature sensor in a two housing portions for connecting them together second housing portion; and for immobilizing them with respect to one anc. connecting the two housing portions to one another for preventing furtherrelative rotation thereother whereby camming faces on one and the other between. housing portion are brought into engagement with 8. A thermostat as defined in claim 1, further comone another; prising a cap made of a good heat conducting material,

(1. subsequent to step (c), rotating the two housing said cap accommodating one of said housing portions portions coaxially with respect to one another for and being crimped firmly onto the other of said housing adjusting the distance between said temperature portions for connecting the housing portions together sensor and said circuit breaker to a predetermined 10 and immobilizing them in their predetermined angular value; and relationship with respect to one another.

e. subsequent 'to step (d), crimping a cap over the 

1. In a thermostat having a first and a second housing portion each having an axis, securing means for holding the two housing portions together, a circuit breaker held in the first housing portion, a snap action temperature sensor held in the second housing portion, an insulating actuating member coupling the temperature sensor to the circuit breaker, the improvement comprising at least one pair of camming faces, said pair being formed of two mutually engaging cooperating faces, one belonging to the one housing portion and the other belonging to the other housing portion, said camming faces being arranged for varying the axial spacing of the two housing portions and the distance between said circuit breaker and said temperature sensor upon coaxial rotation of the two housing portions with respect to one another.
 2. A thermostat as defined in claim 1, wherein said cooperating camming faces have oppositely oriented, wedge-shaped configurations.
 3. A thermostat as defined in claim 2, wherein each housing portion has a plurality of wedge-shaped camming faces to form a plurality of said pairs.
 4. A thermostat as defined in claim 3, wherein said plurality of wedge-shaped camming faces are arranged in immediate succession on each housing portion.
 5. A thermostat as defined in claim 1, wherein said camming faces have a stepped configuration and the cooperating stepped faces have a mutually oppositely oriented pitch.
 6. A thermostat as defined in claim 1, wherein said first and second housing portions have a cylindrical configuration at least in the zone of their respective camming face, each camming face has a radially extending annular configuration and a pitch with respect to said axis.
 7. A method of assembling a thermostat, comprising the following steps: a. mounting a circuit breaker in a first housing portion; b. mounting a snap action temperature sensor in a second housing portion; c. connecting the two housing portions to one another whereby camming faces on one and the other housing portion are brought into engagement with one another; d. subsequent to step (c), rotating the two housing portions coaxially with respect to one another for adjusting the distance between said temperature sensor and said circuit breaker to a predetermined value; and e. subsequent to step (d), crimping a cap over the two housing portions for connecting them together and for immobilizing them with respect to one another for preventing further relative rotation therebetween.
 8. A thermostat as defined in claim 1, further comprising a cap made of a good heat conducting material, said cap accommodating one of said housing portions and being crimped firmly onto the other of said housing portions for connecting the housing portions together and immobilizing them in their predetermined angular relationship with respect to one another. 